TCR Peptide Research Articles

Definition of an extended MHC class II-peptide binding motif for the autoimmune disease-associated Lewis rat RT1.B L molecule

The Lewis rat, an inbred rat strain susceptible to several well-characterized experimental autoimmune diseases, provides a good model to study peptide-mediated immunotherapy. Peptide immunotherapy focussing on the modulation of T cell responses by interfering with TCR–peptide– MHC complex formation requires the elucidation of the molecular basis of TCR–peptide–MHC interactions for an efficient design of modulatory peptides. In the Lewis rat most autoimmuneassociated CD4F T cell responses are MHC class II RT1.BL restricted. In this study, the characteristics of RT1.BL–peptide interactions were explored. A series of substitution analogs of two Lewis rat T cell epitopes was examined in a direct peptide–MHC binding assay on isolated RT1.BL molecules. Furthermore, other autoimmune-related as well as non-disease-related T cell epitopes were tested in the binding assay. This has led to the definition of an extended RT1.BL– peptide binding motif. The RT1.BL–peptide binding motif established in this study is the first described rat MHC–peptide binding motif based on direct MHC–peptide binding experiments. To predict good or intermediate RT1.BL binding peptides, T cell epitope search profiles were deduced from this motif. The motif and search profiles will greatly facilitate the prediction of modulatory peptides based on autoimmune-associated T cell epitopes and the identification of target structures in experimental autoimmune diseases in Lewis rats.

1Prevention of immune dysfunction, vitamin E deficiency, and loss of Cryptosporidium resistance during murine retrovirus infection by T cell receptor peptide immunization

C57BL 6 mice were immunized with peptide corresponding to CDR1 of human T cell receptor (TCR) Vß8.1 and immunoglobulin lambdachain MCG after murine retrovirus (LP-BM5) infection. Immunization with the TCR peptide largely prevented the retrovirus-induced reduction in B and T cell proliferation, tissue vitamin E, and Th1 (T helper 1) cytokine (IL-2 and IFN-τ) secretion. The TCR peptide also prevented retroviral stimulation of Th2 cytokine (IL-6 and IL-10) production and lipid peroxidation. Cryptosporidiosis was established in all retrovirus immunosuppressed mice, while non-retrovirus infected mice were refractory to parasite infection. Cryptosporidium parvum colonization of intestinal villi was significantly reduced in immunosuppressed animals that received TCR Vß8.1 peptide immunization. Thus, immune dysfunction with the loss of parasite resistance, induced by murine retrovirus infection, was largely prevented by TCR Vß CDR1 peptide immunization. However, no significant change in survival of the retrovirally infected mice was observed as the lymph nodes continued to expand which induced eventual death from asphyxiation.

Current and investigational therapies used to alter the course of disease in multiple sclerosis.

Extensive research is under way to develop pharmacotherapeutic agents that will prevent the exacerbations and the progression of neurologic disability associated with multiple sclerosis (MS). The most intensive research strategy has involved agents intended to limit demyelination by reducing inflammation and modifying the immune response. In this category are interferon beta-1b, the first compound approved for use outside of clinical trials; interferon beta-1a; and copolymer 1. Experimental agents include other interferons, methotrexate, linomide, monoclonal antibodies, T-cell receptor peptides, and 2-chlorodeoxyadenosine. Although they have been used effectively to treat exacerbations of MS, corticosteroids and corticotropin are now under evaluation as disease-modifying agents. A second strategy, enhancing remyelination by limiting demyelination and oligodendrocyte injury, is represented by protein growth factors. A third therapeutic approach, improving conduction in demyelinated fibers, is represented by the potassium channel blockers 4-aminopyridine and 3,4-diaminopyridine.

Modulation of experimental allergic encephalomyelitis in mice by immunization with a peptide specific for the gamma delta T cell receptor.

This study investigated the role of gamma delta T cells in experimental allergic encephalomyelitis (EAE), a chronic inflammatory disease of the central nervous system (CNS) that resembles multiple sclerosis. The strategy was to assess the effect on EAE of TCR peptide immunization directed against V gamma 6 T cells, shown recently to predominate in the CNS of mice during the early stages of EAE. The data show that TCR peptide immunization specific for V gamma 6 chains does not induce protection against EAE, since the incidence of EAE in TCR treated animals was similar to control mice, and therefore does not affect disease susceptibility per se, but rather alters the development of the disease. Specifically, there was a delay in the onset of EAE and a reduction in disease severity in TCR treated animals, although the effects were not highly significant. These findings suggest a role for gamma delta T cells in the development of EAE; however, further studies are necessary to confirm the specificity of TCR peptide immunization.

Prevention of retrovirus-induced aberrant cytokine secretion, excessive lipid peroxidation, and tissue vitamin E deficiency by T cell receptor peptide treatments in C57BL/6 mice.

To test whether T cell receptor (TCR) peptide treatment can prevent immune dysfunction, excessive lipid peroxidation, and malnutrition caused by retrovirus infection, female C57BL/6 mice were infected with LP-BM5 retrovirus. Infection with retrovirus inhibited lymphocyte proliferation, cytokine release T helper 1 cells, stimulated cytokine secretion by T helper 2 cells, induced abnormal hepatic and cardiac lipid profiles, and produced excessive tissue lipid peroxidation with hepatic and cardiac vitamin E deficiency. Two weeks after infection, TCR peptides Vbeta5.2, Vbeta8.1, Vbeta8.1 + Vbeta5.2, Vbeta8.1(N), and Vbeta8.1 were injected to the mice at dose of 200 microg/mouse. Vbeta8.1 and Vbeta5.2 treatments largely maintained lymphocyte proliferation and IL-2 and IFN-gamma release, and prevented excessive IL-6, IL-10, and TNF-alpha secretion. Concomitantly, these treatments normalized hepatic and cardiac lipid profiles, reduced tissue lipid peroxidation, and thereby significantly maintained vitamin E in the liver and heart. Vbeta8.1 segments treatment did not prevent the immune dysfunction, abnormal lipid profile and lipid peroxidation, and vitamin E deficiency caused by the retrovirus infection. In conclusion, injection of intact TCR peptides during murine retrovirus infection largely prevented immune dysfunction by blocking the excessive stimulation of a T cell subset caused by retroviral superantigens. It also ameliorated malnutrition status by normalizing lipid profile, lipid peroxidation, and vitamin E deficiency. T cell immune dysfunction and its prevention by TCR peptide treatment is important in the therapy of vitamin E deficiency induced by retrovirus infection.

IL-2 and TNF receptors as targets of regulatory T-T interactions: isolation and characterization of cytokine receptor-reactive T cell lines in the Lewis rat.

T cells are considered to be of prime importance in immune regulation of both B and T cell functions. The targets of recognition in T-T cell interactions are not clear. Most recent experimental work has focused on the idiotypic regulatory interactions mediated by TCR peptides. There is experimental evidence that regulatory cells exist that do not recognize the TCR. This type of regulation is selectively induced by activated T cells. Therefore, we designed this study to examine the possible role of cytokine receptors as targets of immune regulation. We tested two peptides of IL-2R alpha-chain, 2 of IL-2R beta-chain, and one of TNFR (p60). All peptides were found to be immunogenic at inducing T cell proliferation and four induced Abs in Lewis rats. We generated T cell lines to these five peptides, and tested them both in vitro and in vivo. We found that the T cells exhibited a proliferative response when cultured with activated, irradiated stimulator cells that were augmented upon addition of the cytokine receptor peptide. The cytokine profile of the lines was characterized as well as the Vbeta gene composition. One of the lines significantly protected against active encephalomyelitis. These results point at cytokine receptors as possible targets of immune regulation and T-T cell interactions.

Inactivation of T cell receptor peptide-specific CD4 regulatory T cells induces chronic experimental autoimmune encephalomyelitis (EAE).

T cell receptor (TCR)-recognizing regulatory cells, induced after vaccination with self-reactive T cells or TCR peptides, have been shown to prevent autoimmunity. We have asked whether this regulation is involved in the maintenance of peripheral tolerance to myelin basic protein (MBP) in an autoimmune disease model, experimental autoimmune encephalomyelitis (EAE). Antigen-induced EAE in (SJL x B10.PL)F1 mice is transient in that most animals recover permanently from the disease. Most of the initial encephalitogenic T cells recognize MBP Ac1-9 and predominantly use the TCR V beta 8.2 gene segment. In mice recovering from MBP-induced EAE, regulatory CD4+ T cells (Treg) specific for a single immunodominant TCR peptide B5 (76-101) from framework region 3 of the V beta 8.2 chain, become primed. We have earlier shown that cloned B5-reactive Treg can specifically downregulate responses to Ac1-9 and also protect mice from EAE. These CD4 Treg clones predominantly use the TCR V beta 14 or V beta 3 gene segments. Here we have directly tested whether deletion/blocking of the Treg from the peripheral repertoire affects the spontaneous recovery from EAE. Treatment of F1 mice with appropriate V beta-specific monoclonal antibodies resulted in an increase in the severity and duration of the disease; even relapses were seen in one-third to one-half of the Treg-deleted mice. Interestingly, chronic disease in treated mice appears to be due to the presence of Ac1-9-specific T cells. Thus, once self-tolerance to MBP is broken by immunization with the antigen in strong adjuvant, TCR peptide-specific CD4 Treg cells participate in reestablishing peripheral tolerance. Thus, a failure to generate Treg may be implicated in chronic autoimmune conditions.

T-T cellular interaction between CD4-CD8- regulatory T cells and T cell clones presenting TCR peptide. Its implication for TCR vaccination against experimental autoimmune encephalomyelitis.

Regulatory T cells recognizing TCR determinants presumably play a critical role in the control of experimental autoimmune encephalomyelitis, a prototype tissue-specific autoimmune disease. This study was initiated to determine whether regulatory T cells can be induced against a V beta 17a CDR2 peptide (residues 50-68) in SJL/J mice. Although the TCR peptide showed regulatory effects in vivo, the presence of T cells specific for the peptide could not be proven with conventional proliferation assays. Unexpectedly, in the presence of myelin basic protein-specific T clone cells (Tcc), the sensitized spleen cells vigorously proliferated in response to the TCR peptide. The subsequent experiment showed that this was due to the outstanding capability of the Tcc as APC for the exogenous TCR peptide. Using the Tcc as APC, we were able to establish V beta 17a50-68-specific T cell lines from in vivo primed spleen cells. The line cells were MHC class I restricted and dominated by T cells with a distinct surface phenotype (CD4-CD8-V beta 17a+). Presentation of the peptide by the Tcc was inhibited by treatment with gelonin that could block a MHC class I presentation pathway. The ability of T cells to present the TCR peptide was not related to their Ag specificity, but correlated with the expression levels of MHC class I molecules and adhesion molecules such as intercellular adhesion molecule-1 and B7-1 on their surface. The TCR peptide-specific T cells produced a soluble mediator(s) that is inhibitory for T cell activation and were protective against actively induced experimental autoimmune encephalomyelitis. These results show that V beta 17a50-68 vaccination induces regulatory CD4-CD8- T cells that could interact with T cells presenting relevant TCR fragments.

Vitamin E Deficiency and Immune Dysfunction in Retrovirus-Infected C57BL/6 Mice Are Prevented by T-Cell Receptor Peptide Treatment

Female C57BL/6 mice were infected with LP-BM5 retrovirus, causing murine acquired immunodeficiency syndrome (AIDS), which is functionally similar to human AIDS. Retrovirus infection inhibited release of T-helper 1 cytokines, stimulated secretion of T-helper 2 cytokines and induced hepatic and cardiac vitamin E deficiency with increased lipid peroxides. We hypothesized that the immune dysfunction caused increased oxidation and loss of vitamin E. Because T-cell receptor (TCR) peptide treatment blocked the excessive stimulation of a T-cell subset by retroviral superantigens, we tested whether maintenance of normal immune function during infection prevented excessive oxidative damage. The TCR peptide treatments with doses > 100 µg/mouse and administered 2–4 wk postinfection significantly inhibited the retrovirus-induced immune dysfunction, concomitantly reduced tissue oxidative damage and thereby largely maintained vitamin E concentration in the liver and heart. Reducing the dose of peptide or delaying administration until early murine AIDS had developed resulted in severe immune dysfunction that caused elevated tissue lipid peroxidation and loss of vitamin E. The TCR peptide treatment partially maintained production of interleukin-2 (IL-2) and prevented retrovirus-induced elevated production of IL-6 by splenocytes in vitro. In conclusion, TCR peptide treatment during murine retrovirus infection ameliorated immune dysfunction and thus prevented increases in tissue lipid peroxidation and vitamin E loss. T-cell immune dysfunction and its prevention by TCR peptide treatment is important in the therapy of vitamin E deficiency induced by retrovirus infection.

T cell receptor peptides in treatment of autoimmune disease: Rationale and potential

The natural tendency in T cell-mediated autoimmune conditions to develop focused antigen-specific responses that over-utilize certain T cell receptor (TCR) V region segments prompts the induction of anti-TCR-specific T cells and antibodies that can inhibit the pathogenic T cells and promote recovery from disease. This natural regulatory network can be manipulated by injecting synthetic peptide vaccines that correspond to segments of the over-expressed V genes. In experimental autoimmune encephalomyelitis (EAE), an animal model for the human disease multiple sclerosis (MS), the pathogenic T cells are directed at myelin components, including basic protein (MBP). In some strains such as the Lewis rat and the PL/J mouse, the encephalitogenic BP-specific T cells overexpress a particular V region gene (V beta 8.2) in the TCR. In vivo administration of V beta 8.2 peptides in rats or mice can prevent and treat EAE by boosting regulatory anti-V beta 8.2-specific T cells that inhibit but do not delete the encephalitogenic specificities. This regulation is mediated by soluble factors, suggesting that the presence of regulatory TCR-specific T cells within the target organ (the central nervous system) may inhibit not only the stimulating V beta 8.2 + T cells, but also bystander T cells bearing different V genes. Parallel studies in MS patients have revealed striking V gene biases among BP-specific T cell clones from some patients that provided a rationale for TCR peptide therapy. Injection of V beta 5.2 and V beta 6.1 peptides boosted the frequency of TCR peptide-specific T cells and reduced responses to BP, in some cases with clinical benefit, indicating the presence of an anti-TCR regulatory network in humans that may also be manipulated with TCR peptide therapy.

Pretreatment with T Cell Receptor Peptides Using a Conventional Immunization Protocol Does Not Induce Effective Protection against Autoimmune Encephalomyelitis

It was previously reported that vaccination with synthetic peptides corresponding to the CDR2 or CDR3 region of T cell receptor (TCR) protected susceptible animals from the development of experimental autoimmune encephalomyelitis (EAE). However, recent studies by several research groups have revealed that TCR peptide therapy often confers little or no protection from autoimmune diseases. In the present study, we attempted to find more appropriate peptides that is capable of conferring effective protection against the development of EAE. Four peptides corresponding to parts of the Vβ region (13–23, 24–36, 39–59, and 64–74) were selected by epitope scanning and hydrophilicity searching, and their protective abilities were tested. All these peptides were, however, ineffective in protecting rats from the disease. We also generated three different synthetic peptides corresponding to the TCR J region of encephalitogenic T cells. Vaccination with the J-region peptides did not protect animals from the development of EAE. Rather, one of the peptides (Vβ-DSS-Jβ2.6) enhanced the clinical severity of EAE and induced fatal disease in some rats. Taken together, TCR peptide therapy appears to be generally ineffective and elucidation of the mechanism by which EAE is enhanced after TCR peptide vaccination should provide insight into the pathogenesis of this disease.

T-cell receptor peptides that inhibit the T-cell response to allergen induce transforming growth factor-β 1 production

Recent findings indicate restricted usage of T-cell receptor (TcR) β chain variable region 3 (Vβ3) gene elements in the human polyclonal T-cell response to the allergens of house dust mite (HDM).1, 2 Furthermore, we have reported that a peptide analog of TcR-Vβ3 CDR2 specifically inhibits the polyclonal proliferative response of human Vβ3+T cells to unfractionated Dermatophagoides pteronyssinus extract.2 Although the mechanism of inhibition remains to be defined, there is increasing evidence that immunosuppressive cytokines may play an important role in the downregulation of immune responsiveness in a number of experimental systems.

In vivo clonotypic regulation of human myelin basic protein-reactive T cells by T cell vaccination.

Autoreactive T cells specific for myelin basic protein (MBP) are implicated in the pathogenesis of multiple sclerosis. The mechanism by which MBP-reactive T cells are regulated in vivo remains unknown, but is thought to involve the clonotypic regulatory network that can be induced by immunization with attenuated T cells and TCR peptides. We reported previously that immunization of multiple sclerosis patients with irradiated MBP-reactive T cells (T cell vaccination) induced T cell responses to the immunizing clones, resulting in a clonal depletion of circulating MBP-reactive T cells. In this study, we demonstrated that in the majority of the recipients, MBP-reactive T cells remained undetectable in circulation over a period of 1 to 3 yr after vaccination, while they reappeared in some individuals (three of nine), coinciding with clinical exacerbation. The reappearing MBP-reactive T cells were found to originate from clonal origins different from those of T cells persisting before immunization, suggesting a shift of the T cell repertoire to other determinants of MBP. The immunization induces predominantly CD8+ regulatory T cells capable of lysing the immunizing clones in a clonotype-specific manner. The T cell responses induced by immunization were restricted to the immunizing clones and did not affect MBP-reactive clones not used for immunization. Our data further suggest that different hypervariable regions of the TCR may be involved in the observed clonotypic interaction. This study provides useful information for designing future clinical trials using T cell vaccination and other TCR-based therapeutic strategies.

Immunodominant framework region 3 peptide from TCR V beta 8.2 chain controls murine experimental autoimmune encephalomyelitis.

Previous work has demonstrated the existence of regulatory circuitry that controls response to the dominant determinant Ac1-9 of myelin basic protein (MBP) which is highly restricted in TCR V gene usage to V beta 8.2 and V alpha 2.3. In particular, a CD4+ V beta 14+ regulatory T cell was shown to be a vital component of this circuit. In our work presented here, the peptide specificity of the response to V beta 8.2 peptides was examined. Five overlapping peptides, B1 through B5, were studied for their ability to induce a proliferative response: B2 (21-50), B4 (61-90), and B5 (76-101) each had this capacity in the B10.PL or (SJL x B10.PL)F1 mice. The determinant within the TCR peptide B5 appears dominant, whereas determinants within the B2 and B4 peptides are physiologically cryptic. Furthermore, only B5 could down-regulate the response to MBP Ac1-9 and significantly protect mice from MBP- or Ac1-9-induced EAE, whereas B2 or B4 treatment had no significant effect. Treatment of mice with B5 did not result in generalized deletion or inactivation of V beta 8.2+ T cells. The core residues of the B5 determinant lie within framework region 3 of the V beta 8.2 chain and do not include residues from the joining CDR3 region. Response to B5 was restricted by the I-Au MHC molecule. Furthermore, B5 only induced responses in mice with certain MHC alleles. It is evident that by specifically down-regulating the initial dominant response to Ac1-9, Ag-induced disease can be prevented. These data have implications for understanding induction of TCR-based regulation, as well as relevance to possible therapeutic approaches for oligoclonal responses in human autoimmune diseases.

Vaccines to prevent and treat autoimmune diseases.

The current therapy for human autoimmune disease is based on nonselective immunosuppression achieved by corticosteroids or cytotoxic drugs. This form of therapy is toxic and frequently not effective in curing the disease. The study of experimental autoimmune disease models indicates that the pathogenic population of immune cells is restricted in terms of T-cell receptor gene usage and peptide epitopes recognized in the self-antigens. The recent developments in understanding of the pathophysiology of autoimmune disease point to the crucial role of the pathogenic T cell, the autoantigenic peptide, and the major histocompatibility complex molecules as well as the regulatory T-cell population in the disease process. The purpose of this review is to describe the use of vaccines to prevent and treat autoimmune disease. Encouraging results in animal models using vaccines based on the pathogenic T cell or the autoantigen have prompted the design of novel and selective immune-based therapies for human autoimmune disease.

Autoantibodies against peptide-defined epitopes of T-cell receptors in retrovirally infected humans and mice.

Autoantibodies directed against peptide-defined epitopes of T-cell receptors occur in the serum of healthy humans with the levels and isotypic expression dependent upon physiological changes (aging, pregnancy) or upon the development of autoimmune disease. We carried out investigations of autoantibodies against Tcr peptide-defined epitopes in retroviral infections of humans (HIV-1) and mice (LP-BM5 strain of murine leukemia virus) to determine whether infection with these agents disrupted the regulation of the production of these antibodies. Retroviral infection in humans resulted in increased levels of autoantibody production against putative immunoregulatory regions of the Tcr beta chain (V beta CDR1 and Fr3), a result reflecting a disruption of regulation. In addition, antigenic mimicry was observed with a cross-reaction shared between the common portion of the V3 neutralizing loop of the HIV-1 gp120 molecule and the joining segment of T-cell receptors (J beta). Infection of mice with the defective retrovirus resulted in the induction of antibodies directed particularly against V beta CDR1 peptide-defined determinants. Analysis of the virally induced response to a set of 8 CDR1 peptide epitopes indicated a selectivity to the process. It was possible to partially reverse aberrant cytokine changes correlated with the onset of murine MAIDS by administration of T-cell receptor peptides in saline. These results show that retroviral infection in humans and mice has a profound dysfunctional effect on the regulation of autoantibodies to T-cell receptors. The function of these autoantibodies in the immunopathogenesis of acquired immunodeficiency remains to be determined.

Autoregulation of Tcr V region epitopes in autoimmune disease.

Normal individuals possess low levels of autoantibodies specific for certain peptide defined regions of T-cell receptor (Tcr) variable regions, particularly CDR1 and Fr3. These regions are predicted to be exposed on the surface of the native molecule and, by analogy and comparison with immunoglobulins, correspond to public idiotype determinants. The anti-Tcr idiotype antibodies appear to be ubiquitous and we propose that they play a role in the regulation of T-cell function. To delineate the parameters of expression of these antibodies, we characterized anti-Tcr antibody activity in normal individuals, in those suffering from the autoimmune diseases rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE), and in patients with non-autoimmune arthritis (osteoarthritis) as a disease control. There were significant increases in autoantibody levels in the autoimmune patients. There was also variation in isotype and the particular variable regions recognized. IgM autoantibodies directed against a few peptide defined determinants were elevated in RA, whereas SLE patient sera showed high levels of IgG binding to a broad spectrum of Tcr peptides.

Immune Responses against Self-TCR Peptides

Vaccination of rats against the TCR peptide Vβ8.2 (39-59) was reported to inhibit the immunopathogenic process of EAE. Analysis of the immune response to this peptide and several related TCR peptides yielded the following findings: (i) Lewis rats immunized in vivo and challenged in vitro responded with vigorous lymphocyte proliferative responses to peptide Vβ8.2 (39-59) and to three other rat TCR peptides, Vβ8.3 (15-32), Vβ8.3 (39-59), and Vβ14 (39-59). On the other hand, two other rat peptides, Vβ8.2 (18-38) and Vβ8.3 (62-76), were poorly immunogenic. (ii) Rat peptide Vβ8.2 (39-59) was found more immunogenic than its mouse homolog, in both Lewis rats and B10.A mice. A moderate level of cross-reactivity was observed between these two peptide homologs. (iii) Rats of different genetic makeups varied in their response to peptide Vβ8.2 (39-59). A similar pattern of response of the different rats was found with another TCR peptide, Vβ14 (39-59). Hybrids between high and low responder rat strains resembled the high responders in their response to the TCR peptides. (iv) Sensitized lymph node cells as web as lymphocytes of a cell line specific for peptide Vβ8.2 (39-59) failed to respond to T cells that express the Vβ8.2 gene product. This observation is interpreted to indicate that peptide Vβ8.2 (39-59) is a cryptic determinant of the Vβ8.2 protein. Moreover, the data suggest that lymphocytes proliferating against peptide Vβ8.2 (39-59) may not be responsible for the reported inhibition of EAE in rats vaccinated with this peptide.

Coculture of TCR peptide-specific T cells with basic protein-specific T cells inhibits proliferation, IL-3 mRNA, and transfer of experimental autoimmune encephalomyelitis.

TCR peptides, namely V beta 8.2-39-59 or the minimal idiotope, V beta 8-44-54, can treat experimental autoimmune encephalomyelitis (EAE) in Lewis rats, presumably by activating naturally induced TCR peptide-specific T cells that arise in response to the focused appearance of V beta 8.2+ encephalitogenic T cells. The purpose of the present study was to evaluate the mechanisms by which TCR peptides inhibit EAE. We found that treatment of EAE with the V beta 8.2-39-59 peptide did not induce any evidence of DNA fragmentation (apoptosis) in spinal cord cells isolated from clinically well rats, implicating a regulatory rather than a deletional mechanism. TCR peptide-specific T cell lines failed to inhibit EAE induced by already activated BP-specific T cells when the two T cell specificities were co-injected. However, coculturing the encephalitogenic T cells in the presence of the regulatory T cells during the activation step before transfer almost completely inhibited the induction of EAE. Inhibition could be induced by direct contact between the two cell types or by soluble factors produced in a transwell system, but was greatly enhanced when soluble V beta 8.2-39-59 peptide was used to optimally activate the regulatory T cells. The inhibition was regulatory cell dose dependent, and was reflected in vitro by reduced proliferation response and mRNA production for IL-3, and to a lesser extent, IFN-gamma and IL-2. These results indicate that regulation induced by TCR peptides involves cell-cell interactions that lead to the production and release of soluble factors that locally inhibit the activation of encephalitogenic T cells expressing MHC-bound idiotopes of the target V beta-chain, and possibly "bystander" specificities expressing different V beta-chains.

Autoantibodies to the alpha/beta T-cell receptors in human immunodeficiency virus infection: dysregulation and mimicry.

Autoimmune reactivity is a consequence of infection with human immunodeficiency virus (HIV). We studied serological cross-reactions of purified pooled IgG from sera of HIV-infected individuals by using nested sets of synthetic overlapping peptides duplicating the covalent structures of T-cell receptors (TCRs) and immunoglobulin light chains and report that two processes of autoantibody production occur. (i) IgG autoantibodies to putative regulatory variable domain CDR1 and FR3 epitopes (where CDR is complementarity-determining region and FR is framework region) are present in pooled IgG from HIV-infected individuals at levels 10-fold greater than that in pooled IgG from healthy humans. (ii) Anti-TCR autoimmunization involves antigenic mimicry between a conserved peptide stretch of the major neutralizing V3 loop determinant of HIV-1 gp120 and the conserved FR4 segment of the TCR V beta. Affinity-purified antibodies to the synthetic V3 loop peptide bound to a recombinant single-chain TCR and to a synthetic TCR joining segment peptide containing the FR4 sequence. Conversely, affinity-purified autoantibodies from pooled IgG from HIV-infected individuals to the TCR peptide bound the V3 loop peptide and a single-chain TCR. Inhibition studies indicated that the cross-reactive immunizing antigen was the V3 loop. These results bear upon the impact of HIV infection on immune regulation and on the selection of peptides for vaccine development.